1. Field of the Invention
The present invention relates to a method and apparatus for controlling an ion implantation unit.
2. Description of the Related Art
Ion implantation units have been broadly used in manufacture of semiconductor devices, for example, in formation of impurity diffusion regions within a semiconductor substrate.
Generally, an ion implantation apparatus performs an ion implantation upon a lot formed by a plurality of wafers. After an ion implantation operation upon the wafers of one lot is completed, one of the wafers is selected. Then, in order to check the ion implantation operation, the resistance of this selected wafer is measured, and it is determined whether or not the measured resistance is within an allowable range. When the measured resistance is within the allowable range, this lot is transferred to the next process. On the contrary, when the measured resistance is not within the allowable range, this lot is deemed to be defective and is scrapped.
In the prior art, however, when the resistance of one lot is being checked, the ion implantation unit may perform an ion implantation upon the next lot under the same condition. Therefore, when one lot is deemed to be defective, the next lot may also be defective. This means a large number of defective lots may occur.